The present invention generally relates to systems and methods for forming a pipe carcass using multiple strips of material.
Carcass machines produce a carcass of a flexible pipe. A main purpose of the carcass is to prevent the pipe from collapsing under external pressure, e.g., due to water pressure and mechanical crushing during production and installation of the pipe. The collapse strength generally depends on the mechanical integrity of the metal carcass which should withstand the force of the external pressure.
Carcass machines may produce the armor carcass by the process of roll forming and winding of sheet metal strips. For example, a carcass machine may cold-form a flat steel (or other material) strip into an interlocking structure.
Typically, a flat strip of material such as steel is pulled off of a coil and is run through a series of deforming operations to form a profile of the interlocking structure. These operations are performed by pressers or rollers that gradually change the profile of the strip, and subsequent to the generation of such a strip, a winding step is used during the manufacture of the carcass for the flexible pipe body. In some examples, the carcass strip is formed into a profile having hook and valley regions, so that as the strip of material is wound, adjacent windings are interlocked together by nesting hook and valley regions. During manufacture, the shaped strip may be wound at an angle, so that the flexibility of the metal carcass produced allows the metal carcass sufficient flexibility.
It has been observed that flow-induced pulsation may occur in the flexible pipe, particularly near the open spaces of the metal carcass. The interaction between fluid flow and inner carcass geometry, among other factors, may lead to increased fatigue that affects the lifespan of the piping, particularly when used in underwater applications.